Estimating the minimal clinically important difference for the Physical Component Summary of the Short Form 36 for patients with stroke

OBJECTIVE: To determine the Physical Component Summary (PCS) score's minimal clinically important difference (MCID) on the Short Form 36 (SF-36) for people with stroke. METHODS: We conducted secondary analysis of data from a large randomized controlled trial (N = 400) in the post-hospital discharge phase of stroke rehabilitation with outcome measurement 6 and 12 months following stroke. Three methods were used for estimating the MCID: two anchor and one distribution. Method 1 compared SF-36 PCS scores at 12 months for responses to the SF-36's Perceived Health Change (PHC) question. Method 2 compared the change in PCS score between 6 and 12 months for responses to the PHC question. Method 3 used Cohen's method to estimate the MCID from the PCS score distribution. RESULTS: Method 1: the mean PCS score increased by 3.0 units (95% confidence interval [CI] 2.2-3.9) for each unit change in the PHC question. Method 2: the mean change in PCS score increased by 2.1 units (95% CI 1.4-2.8) for each unit change in the PHC question. Method 3: the MCID was estimated to be 1.8 units. CONCLUSIONS: Our estimate of the MCID for the PCS in patients with stroke was 1.8 to 3.0 units.